The present invention relates generally to prosthetic implants and pertains, more specifically, to the implant of acetabular cup assemblies which secure a prosthetic bearing member in the acetabulum for the reception of a femoral head of a prosthetic hip joint.
The replacement of members of a natural hip joint with prosthetic implants has become widespread and is being accomplished with ever-increasing frequency. The variety of conditions encountered when effecting such implants has led to the use of various bearing materials placed at an optimum position and orientation, as determined by conditions encountered at the site of the implant. The choice of a particular material for the bearing, as well as the size, positioning and orientation of the bearing member, is determined by the surgeon performing the procedure. Usually such choices are made on the basis of a pre-operative assessment of the needs of a particular patient; however, at times the choices are not completed until the implant site actually is being prepared and conditions encountered at the site can be evaluated during the implant procedure itself. Accordingly, it would be advantageous to have available a greater range of interoperative choice, as well as pre-operative choice, so as to enable a surgeon to accommodate the needs of a particular patient as determined by either or both a pre-operative assessment and an evaluation of conditions encountered at a particular implant site, and to do so in a practical manner.
The present invention provides the surgeon with the ability to choose, either pre-operatively or interoperatively, an optimum material, position and orientation for a bearing member of an acetabular cup assembly to be implanted at a particular implant site, with increased ease and at lowered expense. As such, the present invention attains several objects and advantages, some of which are summarized as follows: Accommodates a wider choice of bearing materials in the bearing member of an acetabular cup assembly, while utilizing a common acetabular shell; enables the choice of size, position and orientation of the bearing surface of a bearing member selected for assembly with a particular acetabular shell; increases the range of bearing materials, as well as bearing size, positioning and orientation, and renders the choices available in a practical manner for either pre-operative or interoperative selection; allows a surgeon greater latitude in accommodating the needs of different patients while meeting the requirements imposed by various conditions encountered at a particular implant site, and enables appropriate choices to be made interoperatively, as well as pre-operatively; promotes greater accuracy in the replacement of a natural hip joint, with increased economy; provides a surgeon with the ability to make both pre-operative choices and interoperative choices from a wider range of options; enables the securement of a bearing member of selected material within a common acetabular shell, with increased ease and economy, and without complex, specialized instruments; facilitates the insertion and securement of a selected bearing member within an acetabular shell in appropriate alignment and orientation of the bearing member within the acetabular shell; provides an acetabular cup assembly having a bearing member of appropriate bearing material and accurate sizing, positioning and orientation, with economy of manufacture and use, and long-term reliability.
The above objects and advantages, as well as further objects and advantages, are attained by the present invention which may be described briefly as an acetabular cup assembly for receiving a proximal end of a femoral component of a prosthetic hip implant, the femoral component including a head member and a neck member depending from the head member, the acetabular cup assembly having an external shell member with an internal cavity, and an internal bearing member for securement within the cavity to receive the head member of the femoral component for rotational movement within the bearing member, the internal bearing member being selected from a plurality of bearing members having different characteristics such that the acetabular cup assembly selectively is provided with characteristics corresponding to the characteristics of the selected internal bearing member, the acetabular cup assembly comprising: a metallic securing member for reception within the cavity of the acetabular shell, the securing member extending between and upper end and a lower end and including an external securing element and an internal receptor element; an external receptor element on the bearing member, the external receptor element and the internal receptor element being compatible with particular characteristics of the bearing member such that upon engagement of the external receptor element with the internal receptor element the internal bearing member is secured to the securing member with the lower end of the bearing member spaced upwardly a prescribed distance from the lower end of the securing member; and an internal securing element within the cavity of the shell member, the internal securing element being essentially complementary to the external securing element of the securing member such that upon selective engagement of the external securing element with the internal securing element the securing member is secured selectively within the shell member; the prescribed distance between the lower end of the bearing member and the lower end of the securing member being such that contact between the neck member of the femoral component and the lower end of the securing member precludes deleterious impingement of the femoral component upon the bearing member.
Further, the present invention provides a shell member for use in an acetabular cup assembly having an internal bearing member for securement within the shell member, the internal bearing member being selected from a plurality of bearing members having different characteristics such that the acetabular cup assembly selectively is provided with characteristics corresponding to the characteristics of the selected internal bearing member, the shell member comprising: an internal cavity; a first securing element within the cavity of the shell member, the first securing element being compatible with the securing characteristics of at least one of the plurality of internal bearing members; and a second securing element within the cavity of the shell member, the second securing element being compatible with the securing characteristics of at least another of the plurality of internal bearing members; the first and second securing elements being juxtaposed with one another and placed at relative locations such that the effectiveness of each of the first and second securing elements is maintained in the presence of the other of the first and second securing elements, whereby the one and the another of the internal bearing members each is selectable for effective securement within the shell member to complete the acetabular cup assembly.
In addition, the present invention includes a kit of component parts for assembling an acetabular cup assembly having an internal bearing member secured within a shell member, the kit comprising: a plurality of bearing members having different characteristics such that the acetabular cup assembly selectively is provided with characteristics corresponding to the characteristics of a selected one of the internal bearing members; the shell member comprising: an internal cavity; a first securing element within the cavity of the shell member, the first securing element being compatible with the securing characteristics of at least one of the plurality of internal bearing members; and a second securing element within the cavity of the shell member, the second securing element being compatible with the securing characteristics of at least another of the plurality of internal bearing members; the first and second securing elements being juxtaposed with one another and placed at relative locations such that the effectiveness of each of the first and second securing elements is maintained in the presence of the other of the first and second securing elements, whereby the one and the another of the internal bearing members each is selectable for effective securement within the shell member as the selected one bearing member to complete the acetabular cup assembly.
Still further, the present invention provides an improvement in a method for implanting an acetabular cup assembly having an external shell member with an internal cavity, and an internal bearing member for securement within the cavity, the internal bearing member being selected from a plurality of bearing members having different characteristics such that the acetabular cup assembly selectively is provided with characteristics corresponding to the characteristics of the selected internal bearing member, the improvement comprising the steps of: providing a first securing element within the cavity of the shell member, the first securing element being compatible with the securing characteristics of at least one of the plurality of internal bearing members; providing a second securing element within the cavity of the shell member, the second securing element being compatible with the securing characteristics of at least another of the plurality of internal bearing members; and selecting the one or the another of the internal bearing members and securing the selected internal bearing member within the shell member by engaging the selected internal bearing member with the corresponding first securing element or second securing element for completion of the acetabular cup assembly.